Weekly scan: pericyte HGF, human pancreatic interfaces, and the vascularization gap
A strict-window scan of four new papers separating vascular-MPS methods, pancreatic vascular-niche biology, native beta-cell/endothelial interfaces, and transplant immune outcomes from direct graft-vascularization evidence.
Window check
This issue covers papers recorded from 2026-08-17 08:00 through 2026-08-24 08:00 (UTC+01:00). Four peer-reviewed records fall inside that window: a human BBB-immune microphysiological platform dated 18 August, two pancreatic vascular-interface studies dated 19 August, and a multicentre islet-transplant study dated 17 August. 1234
The week separates into four evidence types:
- Vessel-on-chip / vascular-MPS methods: one human BBB-immune platform, adjacent to the pancreatic focus.
- Pancreatic vascular niche: one pericyte-derived trophic-factor study.
- Human beta-cell/endothelial interface: one native-tissue expression study.
- Transplant context: one immune-regimen study with clinical engraftment and metabolic endpoints.
No verified paper in the window directly tested an islet-context vessel-on-chip intervention, improved revascularization of transplanted islets, or vascularization efficacy for stem-cell-derived beta-cell or SC-islet grafts. The four papers below therefore support experimental design and evidence triage around the gap rather than closing it.
1. A BBB-immune chip separates barrier transport from immune response
Identification of Pro-Atherogenic Microenvironment-Associated Molecular Signatures in Response to Key Effective PM2.5 Constituents Using a Blood-Brain Barrier-Immune Microenvironment Platform — Yueyi Li and colleagues, Environmental Science & Technology, PubMed record dated 18 August 2026. 1
System / model
The authors built a human blood-brain barrier-immune microenvironment platform for dynamic PM2.5 exposure. The platform uses compartment-resolved measurements to follow constituent movement across the barrier and responses on the brain side. The model includes astrocyte and microglial readouts alongside barrier behavior. 1
Key finding
High PM2.5 doses increased barrier permeability and constituent translocation into the brain-side compartment. The translocated material was associated with astrocyte reactivity, microglial M1 polarization, elevated reactive oxygen species, neuroinflammatory responses, lipid dysregulation, and impaired barrier maintenance. Chromium and the water-soluble organic matter fraction, including the reported constituents C28H7O2N and C21H16N2SP2, showed the strongest associations with these responses. The PubMed abstract reports no effect sizes or sample counts. 1
Why it matters
The platform keeps transport, barrier integrity, and immune-state readouts in separate compartments. That separation is useful for vascular-MPS work because a change in a downstream cell state can be compared with the amount and composition of material that crossed the endothelial interface. The design points toward a practical rule for vascular-chip experiments: report perfusion or permeability together with compartment-specific cell responses.
Main caveat
The model represents a human BBB-immune interface exposed to an environmental mixture. It supplies methods evidence for vascular microphysiological systems, while the islet niche, pancreatic endothelial subtypes, and graft-revascularization endpoints remain outside the study. The component-level associations also require mechanistic validation before they can guide a pancreatic intervention.
Original source: PubMed record for the paper · Journal DOI
2. Pancreatic pericytes supply HGF to support beta-cell function
HGF Endogenously Produced by Pancreatic Pericytes Regulates β-Cell Function — Shani Puyesky and colleagues, Diabetes, PubMed record dated 19 August 2026. 2
System / model
The study examines human and mouse islets, identifies the endogenous source of hepatocyte growth factor, and tests the physiological requirement for pericytic HGF in vivo. The abstract also describes roles during embryonic development and pregnancy-related beta-cell mass expansion. Exact sample counts and effect sizes are not reported in the PubMed abstract. 2
Key finding
Pancreatic pericytes were identified as the primary endogenous HGF source in human and mouse islets. Loss of pericytic HGF caused glucose intolerance and impaired insulin production through changes in beta-cell gene regulation. Mesenchymal or pericytic HGF also supported beta-cell mass establishment during embryogenesis and pregnancy. 2
Why it matters
The result gives vascular support cells a functional role in the endocrine niche. For engineered islet or beta-cell grafts, pericytes can be evaluated as sources of trophic signals alongside their structural role around endothelial cells. A vascularization strategy that measures vessel density alone could miss this pericyte-to-beta-cell signaling layer.
Main caveat
The reported endpoints are pericyte-derived HGF, beta-cell gene regulation, insulin production, glucose tolerance, and beta-cell mass. The study record provides vascular-niche biology rather than a graft-revascularization intervention, perfusion measurement, or transplant comparison. Adding HGF or pericytes to a stem-cell-derived islet graft therefore remains an experimental hypothesis.
Original source: PubMed record for the paper · Journal DOI
3. Human pancreatic tissue places Cx31.9 at both beta-cell and vascular interfaces
Connexin 31.9 is expressed in human pancreatic endocrine beta cells, as well as in exocrine ductal epithelial and vascular endothelial cells — Elia Martha Pérez-Armendariz and colleagues, Bioscience Reports, PubMed record dated 19 August 2026. 3
System / model
The authors analyzed sections from 23 human pancreatic autopsy samples using real-time qRT-PCR and immunohistochemistry. The qRT-PCR analysis used seven pancreases. The IHC analysis included 16 donor samples for islet-cell staining and 31 islet images from 10 donors for staining-density quantification. 3
Key finding
Cx31.9 mRNA levels were similar to the Cx36 control gene in the seven analyzed pancreases, with P = 0.7854. Cx31.9-positive staining appeared in islet cells in 15 of 16 donor samples. The authors quantified staining across 31 islet images from 10 donors, with a median integrated density of 1324.96 and a range of 19.97 to 3931.5. Serial sections placed Cx31.9-positive cells near insulin- and Cx36-positive cells, while endothelial cells in small, medium, and large vessels also stained for Cx31.9. 3
Why it matters
The study maps one candidate communication protein across endocrine, ductal, and vascular compartments in native human pancreas. That map can inform marker selection for beta-cell/endothelial co-culture and for checking whether an engineered interface resembles native tissue. The study adds a human reference layer to the pericyte-HGF result, which concerns vascular trophic signaling.
Main caveat
The evidence comes from archival human tissue expression and staining. The study includes no Cx31.9 perturbation, perfusion assay, transplantation model, or vascularization intervention. Expression across compartments therefore supports interface biology, while its contribution to graft survival or vessel formation remains unresolved.
Original source: PubMed record for the paper · Journal DOI
4. Immunosuppression changes transplant outcomes without isolating vessel formation
A multi-centre study of belatacept and sirolimus for islet transplantation — Natasha Rogers and colleagues, Diabetologia, PubMed record dated 17 August 2026. 4
System / model
This non-randomised, phase 2, multicentre, open-label clinical study compared belatacept plus sirolimus with tacrolimus plus mycophenolate mofetil. Nine people with type 1 diabetes received belatacept/sirolimus and 24 people formed the contemporaneous tacrolimus/mycophenolate cohort. All participants had received at least one islet transplant. 4
Key finding
The primary endpoint combined freedom from hypoglycaemia, positive C-peptide, and HbA1c below 53 mmol/mol (7.0%) at 12 months after the first transplant. Eight of nine belatacept/sirolimus participants (89%) reached the endpoint, compared with 12 of 24 (52%) in the tacrolimus/mycophenolate cohort. HbA1c, hypoglycaemia scores, and insulin requirements fell in both groups. Renal function remained unchanged only in the belatacept/sirolimus group, and CD4+FOXP3+ regulatory T-cell proportions were higher in that group. 4
Why it matters
Clinical graft function reflects several processes at once: immune injury, engraftment, endocrine cell survival, and tissue perfusion. This study shows why a better transplant outcome cannot be assigned to vascularization without a vessel-specific endpoint. For vascularization experiments, immune regimen and engraftment timing belong in the list of measured or controlled variables.
Main caveat
The study is non-randomised and uses small treatment cohorts with a contemporaneous comparator. Its primary outcome is a clinical metabolic and hypoglycaemia endpoint. The abstract reports early engraftment, while the study does not provide a direct measurement of graft vessel formation or revascularization. Individual participant data are unavailable.
Original source: PubMed record for the paper · Journal DOI
What this week changes
The four papers answer four different experimental questions:
- The BBB-immune platform asks whether a vascular barrier can be linked to compartment-specific transport and immune responses.
- The pancreatic pericyte study asks which vascular support cell supplies a trophic signal required for beta-cell function.
- The Cx31.9 study asks which communication marker appears across native human endocrine and vascular compartments.
- The transplant study asks whether an immune regimen improves clinical graft outcomes.
Together, the papers support a layered design for future islet-vascularization work. Measure perfusion or barrier transport, vascular-cell trophic signaling, beta-cell function, immune injury, and graft vessel formation as separate readouts. A higher C-peptide result, a denser endothelial marker, or a responsive chip compartment alone cannot substitute for direct evidence that a transplanted islet or stem-cell-derived islet has formed a functional vascular connection.
For this strict week, the direct evidence gap remains: no verified record tested an islet-context vessel-on-chip intervention, improved vascularization of an islet transplant, or vascularization efficacy for a stem-cell-derived beta-cell or SC-islet graft. The most actionable new signal is therefore the pericyte-HGF link, while the chip and clinical papers define measurement and attribution constraints around it.
References
- 1
- 2HGF Endogenously Produced by Pancreatic Pericytes Regulates β-Cell Function
pubmed.ncbi.nlm.nih.gov
- 3
- 4A multi-centre study of belatacept and sirolimus for islet transplantation
pubmed.ncbi.nlm.nih.gov
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